Many metallic cans for holding beverages or other products are provided with easy-open can ends, wherein a pull tab attached to a tear strip that is defined by a score line in the can end may be pulled to provide an opening in the can end for dispensing the can's contents. Likewise, many food products are sold in metal containers that have ends designed to facilitate access to the contents without the use of can openers or the like.
By way of example, in the manufacture of an easy-open can end, a can end shell is first formed from a metal sheet product, preferably an aluminum sheet product. The can end shell is then conveyed to a conversion press. In the typical operation of a conversion press, a can end shell is introduced between an upper tool member and a lower tool member which are in the open, spaced apart position. A press ram advances the upper tool member toward the lower tool member in order to perform any of a variety of tooling operations such as rivet forming, paneling, scoring, embossing, tab securing, and final staking. After performing a tooling operation, the press ram retracts until the upper tool member and lower tool member are once again in the open, spaced apart position. The partially converted shell is transported to the next successive tooling operation until an easy-open can end is completely formed and discharged from the press. As one shell leaves a given tooling operation, another shell is introduced into or indexed into the vacated operation, thus continuously repeating the entire easy-open can end manufacturing process. Conversion presses can operate at speeds that produce in excess of 500 can ends per minute. It has been the practice in the can end industry to maintain the metal gauge of the can end to a gauge of approximately 0.0108 to 0.0116 inch. As can be appreciated, the very nature of can end formation requires a nearly continuous monitoring of the output of the press in order to maintain product quality and avoid situations in which the die tooling is subject to damaging misalignment or wear conditions that result in poor quality products. It is a goal of the conversion press industry to continue to strive toward the manufacture of can ends of both reduced diameter and reduced metal thickness in order to effect enhanced cost savings through the use of less metal in each packaged product. Likewise, it is another goal of the industry to maintain product quality at the highest rates of press operation and to minimize the loss of product due to undetected die wear and/or die failure.
It is therefore an object of this invention to provide a conversion die tooling wear, press operation, and product quality monitoring method and apparatus.
It is yet another object of this invention to provide a method and apparatus for identifying unacceptable part quality or conditions that could damage the conversion press during operation and to identify such parts or indicate the need to immediately stop the conversion press.